Elongated roadway luminaire



Sept. 13, 1955 c. H. REX

ELONGATED ROADWAY LUMINAIRE 2 Sheets-'Sheet l Filed Aug. 16, 1950 NNVN X :e PR LMH. e5 V@ mw Sept 13 1955 c. H. REX 2,717,954

ELONGATED ROADWAY LUMINAIRE Filed Aug. 16, 1950 2 Sheets-SheetI 2 Figs. Z0

Y /75/ Pfl/waan inventor: Charles H. Rex,

-ls Attorneg.

United States Patent() ELONGATED RGADWAY LUMINAIRE Charles H. Rex, Marblehead, Mass., assigner to General Electric Company, a corporation of New York Application August 16, 1950, Serial N 179,6@

Claims. (Cl. 240-25) My invention relates to luminaires, and more particularly to cylindrical, elongated luminaires adapted to receive one or more elongated tubular light sources, such as fluorescent lamps. The invention is especially applicable to street or roadway luminaires of the lluorescent lamp type.

For roadway illumination it is desirable to project a wide flat beam of light downwardly and along the roadway; or, if the luminaire is mounted at one side of the roadway, the wide light beam should be directed downwardly and obliquely across the roadway. For this purpose a fluorescent source, being considerably elongated, is well adapted. With such a source utilized in a unilateral luminaire, it is necessary to control the beam in the vertical plane only, lateral spreading of the beam being unnecessary and lateral direction being provided by orientation of the luminaire itself. The large source area of a fluorescent source is also desirable in street lighting because of its consequently reduced brightness. Elongated cylindrical unilateral luminaires are particularly well adapted for mounting in pairs at the side of a roadway, where they may be mounted in diverging back-to-back relation to provide oppositely directed asymmetric beams without special design of the individual units of the pair.

Accordingly, therefore, it is a general object of my invention to provide a new and improved elongated cylindrical luminaire particularly adapted for street or roadway illumination.

It is still another object of my invention to provide a new and improved street or roadway luminaire having a large source area and low source brightness.

lt is still another object of my invention to provide a new and improved cylindrical, inverted trough-shaped luminaire adapted to project a vertically concentrated band of light without redirecting any appreciable amount of the reilected light through the light source.

A further object of my invention is the provision of a new and improved cylindrical, inverted trough-shaped luminaire arranged to project unilaterally therefrom a 'vertically concentrated beam of light from either one or two elongated tubular light sources of the fluorescent lamp type.

It is still another object of my invention to provide new and novel means for assembling a cylindrical troughshaped reflector together with a transparent cover plate overlying the open face of the reilector.

A still further object of my invention is the provision of a new and novel roadway luminaire adapted for side mounting and arranged to project obliquely along the roadway in opposite directions broad main beams of light at high angles above the vertical to the nadir.

In carrying out my invention in one form I provide a pair of elongated cylindrical lighting units, or luminaires, of the unilateral type, mounted in diverging back-to-back relation. Each luminaire unit comprises an elongated cylindrical reflector of generally spiral cross-sectional configuration and adapted to receive in the upper portion of smallest radius of curvature an elongated light source.

The reflector has a main rear portion of parabolic configuration arranged to project a wide main beam of parallel light through the open front face, and an upper portion of elliptical configuration curving behind and over the light source to redirect light from the source generally into the main beam without redirection through the source.

My invention itself will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing, in which Fig. l is a top or plan view of a dual-unit roadway luminaire adapted for roadside mounting and embodying by invention; Fig. 2 is a side elevational view of the luminaire shown at Fig. l; Fig. 3 is a side elevational view, partly in section, of one of the luminaire units illustrated at Figs. l and 2; and Fig. 4 is an enlarged crosssectional View of the luminaire unit shown at Fig. 3, taken along the line 4 4 of Fig. 3 and illustrating the optical characteristics of the luminaire.

Referring now to the drawing, I have illustrated at Figs. l and 2 a dual-unit side-mounted roadway luminaire including a pair of cylindrical, elongated inverted troughshaped luminaire units il@ and il disposed in diverging back-to-bacl; relation, each unit being arranged to project unilaterally along and obliquely across the roadway a wide light beam vertically concentrated at high angles from the vertical to the nadir. The elongated luminaire units l@ and ii are each fixed at one end to supporting pipes i2 and i3 mounted upon a pole i4, and are supported at their outer ends by a pair of tie-rods 15 and 16 fixed to the pole.

Each luminaire unit comprises an inverted troughshaped cylindrical reflector 17, formed for convenience in two sections disposed in end-to-end relation and connected by a collar 13. rl`he rellectors 17 may be formed of any suitable light reflecting material, such as polished sheet metal having a specular reilecting surface. The reilectors 17 are of generally spiral transverse crosssectional conguration, as will be more fully described hereinafter, and present at one side between their upper and lower longitudinal edges an open front face enclosed by a transparent cover 19. The cover 19 may, by way of example, be formed of glass or of any desired transparent plastic material. The rellector and cover of each luminaire unit are held together in assembled relation by a pair of end plates 20 which are tied together by connecting rods or bars 21, 22 and 23. The rod 23 is a tie rod located behind the reflector and illustrated at Figs. 3 and 4. The bars or rods 21 and 22 serve also to connect together the rellector 17 and cover i9 in assembled relation, as will be more fully described hereinafter.

Referring now more particularly to Figs. 3 and 4, l have there shown in greater detail one of the luminaire units, i. e. the unit 1l, shown at Figs. l and 2. Fig. 3 is a rear view of such unit, partly in section, showing the cylindrical elongated reflector sections 17 mounted at their ends in the end plates 20 and the intermediate connecting collar 18. For this purpose the end plates 20 and the connecting collar 18 are slotted along curves corresponding to the transverse cross-sectional coniiguration of the retlector sections, and the reflector sections are set into these slots and sealed in place by suitable resilient gaskets 24. On the front side of the reflector the transparent cover plate 19 is similarly mounted and sealed in the end plate 2i) and the connecting collar 18. The end plates 2l) are held together by the tie rod 23 and also by the connecting bars 21 and 22. The bars 21 and 22 are longitudinally slotted, as illustrated at Fig. 4, and positioned in interlocking tongue and groove relation between adjacent longitudinal edges of the transparent cover plate 19 and the reflector 17. As illustrated at Fig. 3, the slotted con- 3 necting bars 21 and 22 are fixed to the end plates 20 by bolts 25, and thus serve not only to support the cover glass 19 in the reflector face but also to tie together the end plates 20 and hold the entire luminaire in assembled relation.

The connecting bar 21, being disposed on the upper longitudinal edge of the reflector, has a cross-section particularly designed to prevent the entrance of water into the luminaire. For this purpose the upper front reflector edge 17a is formed to provide an inturned reentrant lip, the slotted bar 21 interlocking with the inner edge of the lip at 21a and having a downwardly sloped upper surface 2lb abutting the lower side of the inturned lip. This sloping edge allows water to run off without backing up and entering the luminaire.

Referring particularly to Fig. 3, it will be observed that the interior face of each end plate 20 is provided with two mounting brackets 26 upon each of which is supported a lamp socket 27, the sockets being arranged in oppositely disposed and aligned pairs. The oppositely disposed pairs of sockets 27 are adapted to receive elongated tubular lamps 28 and 29, which may suitably be of the fluorescent type. Electrical connections for the lamps (not shown) may suitably be made through the mounting pipe 12 and a flanged connecting collar 12a bolted to the end plate 20 on the pole end of the luminaire. To provide for mounting and disrnounting of the lamps 28 and 29 within the luminaire, the end plate 20 adjacent the pole is provided with a hand hole or aperture covered by a hinged door 30.

Referring now more particularly to Fig. 4, it will be observed that each cylindrical reflector section 17 is generally spiral in transverse cross-sectional configuration with its portion of small radius of curvature at the top, thereby to provide a main lower reflector portion at the rear opposite an open front face and a curved top reflector portion extending over and at least partially shielding the lamps 2S and 29. Between those longitudinal edges of the reflector 17 defining the open front face of the reflector there is supported by means of the slotted connecting bars 21 and 22 the transparent cover plate 19. The lamps 28 and 29 thus being mounted in the upper and more constricted portion of the reflector are kept warm by heat retained in this upper portion.

The lower rear or main portion of the generally spiral reflector 17 is of parabolic configuration from a level only slightly below the front upper edge of the reflector to the bottom of the reflector. This parabolic section has its focal point within the reflector adjacent the upper limit of the parabolic section and toward the front of the reflector. The locus of the parabolic focal points taken along the length of the elongated reflector defines a parabolic focal line extending longitudinally of the reflector and indicated at Fo Fig. 4. The light source 28 is mounted with its axis substantially coincident with this parabolic focal line Fo. The parabolic axes of the rear parabolic lower reflector sections are inclined at a small acute angle below the horizontal, and the loci of these axes taken along the length of the elongated reflector define parabolic axial planes passing through the focal line F and parallel to the reflected light lines 31, 32 and 33 shown at Fig. 4. Preferably these parabolic axes are inclined at about 75 degrees above the vertical to the nadir, as indicated at Fig. 4. The lines 31, 32 and 33 represent beams projected from the source 28 along lines 31a, 32a and 33a, respectively, and reflected from various parts of the rear parabolic reflector portion. This lower rear portion of the reflector 17, then, redirects light from the source 28 along parallel lines defining a main downwardly directed beam of concentrated light disposed at a high angle above the vertical to the nadir.

Above the parabolic lower portion of the reflector 17 the reflector curves upwardly and forwardly over the top of the light sources 28 and 29 in an elliptical curve approaching the focal line F0. The elliptical top portion of the reflector is connected to form a smooth continuous surface with the parabolic portion, and comprises a plurality of adjacent elliptical segments all of which have their primary foci on the parabolic focal line Fo. Thus, the primary foci of the elliptical top portion of the reflector, taken along the length of the reflector, define a primary focal line coincident with the parabolic focal line F0. The adjacent elliptical segments of the reflector top are numbered 1 to 5 inclusive, progressing from the rear of the reflector over the top and around to the upper front edge. Each of the elliptical segments 1 to 5, inclusive, is so shaped and oriented that its secondary focus is spaced apart by a predetermined distance from the parabolic and primary focal line Fo. The loci of the secondary foci, taken along the length of the elongated reflector, thus define a plurality of secondary focal lines lying in parallel spaced relation with respect to the primary focal line F0. In the illustrated embodiment of the invention the secondary focal lines are indicated at Fig. 4 by the points F1, F2, F3, F4 and F5, corresponding respectively to the elliptical sections 1, 2, 3, 4 and 5. It will be observed that the secondary focal lines F1 to F5, inclusive, are substantially equally radially spaced from the primary focal line F0 and lie generally behind and above the focal line Fo, the secondary focal lines thus lying along an arc of an imaginary substantially circular cylindrical surface disposed generally behind and above the focal line Fo. These secondary focal lines progress around the primary and parabolic focal line Fo sequentially and in the same rotational order as their associated reflector segments 1 to 5.

At Fig. 4 I have indicated, by direct and reflected light lines, the manner of redirection of light by each of the elliptical segments 1 to 4, inclusive, the small segment 5` being omitted to avoid confusion on the diagram. By the lines 34 and 35 I have indicated that light from the source emanating along the line 34 and striking the elliptical section 1 is redirected by single reflection out of the luminaire through the open front face of the reflector and along a line 35 disposed at approximately 44 degrees above the vertical to the nadir. Light from this elliptical section 1, therefore, is directed lower than the main parabolic beam, and serves to build up the illumination of an area closer to the luminaire than that toward which the main parabolic beam is directed. Similarly, light reflected from the lower or rear end of the elliptical section 2 and passing through the secondary focal line F2 serves to further build up this illumination close to and immediately below the luminaire.

Light emanating from the source 28 along lines 36 and 37 and reflected by the front part of the elliptical segment 3 and the upper or front part of the elliptical segment 2 is redirected through the secondary focal lines F3 and F2, respectively, along lines 38 and 39, respectively, whereupon it is redirected by secondary reflection along lines 40 and 41, respectively. This secondarily reflected light is thus directed into the main beam at various angles apprcciably above the vertical to nadir, as indicated diagrammatically at Fig. 4.

Finally, light projected from the source 28 along line 42 to the front part of the elliptical segment 4 is reflected along line 43 through the focal line F4 and then by secondary reflection along the line 44 to the bottom of the reflector, whereupon it is projected by a third reflection along line 45 slightly below the main beam. Light from the source 28 falling upon the last elliptical section 5 is similarly redirected, but has not been shown to avoid confusion in the diagram.

It will now be observed that all light emanating from the source 28 and redirected by the reflector, either by single reflection or multiple reflection, is projected out through the open face of the reflector without passing through the envelope of the tubular light source 28. It is highly desirable to avoid passing reflected light through the light source, since the intensity of reflected light is considerably reduced and the temperature of the lamp envelope is undesirably increased by such passage of reflected light through the source. It is principally for this purpose that the secondary focal lines F1 to F5, inclusive, of the elliptical segments 1 to 5, inclusive, are disposed, as described, in parallel spaced relation with respect to the primary and parabolic focal line Fo.

I have also indicated at Fig. 4 that, if desired, a second light source 29 may be positioned eccentrically with respect to the main focal line F0 of the reflector, but behind and above the principal light source 28 in such a position that it adds to the total illumination emanating from the reflector without appreciably disturbing the light distribution described above. By reason of the eccentric and elevated location of the secondary light source 29, it will now be evident that light from this source is somewhat divcrsely reflected, and in general is directed below the main parabolic beam originating at the beam source 28 and projected by the main lower reflector portion. The secondary light source 29 thus serves principally to build up the amount of illumination below the luminaire and at points between the luminaire and the remote portions of the roadway lighting pattern defined by the main parallel beam.

While I have described only a preferred embodiment of my invention by way of illustration, many modifications will occur to those skilled in the art, and I, therefore, wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the truc spirit and scope of my invention.

What l claim as new and desire to secure by Letters Patent of the United States is:

1. A roadway luminaire adapted to receive an elongated tubular light source and comprising a cylindrical inverted trough-shaped reflector having a generally spiral transverse cross-sectional configuration and an open front face, the lower rear portion of said reflector opposite said front face being parabolic in cross-section and having a parabolic focal line lying within said reflector adjacent the upper limit of said lower portion, the upper portion of said reflector being elliptical in cross-section and having a primary focal line substantially coincident with said parabolic focal line, said upper portion joining said lower portion to form a continuous curved surface extending upward and horizontally over said focal lines and coi rprising a plurality of adjacent elliptic segments having secondary focal lines lying within said reflector and positioned in parallel spaced relation with said primary focal line, and means for mounting in said reflector an elongated tubular light source disposed with its axis substai-- tially coincident with said parabolic focal line.

2. A roadway luminaire adapted to receive an elongated tubular light source and comprising a cylindrical inverted trough-shaped reflector having a generally spiral transverse cross-sectional configuration and an open froiif: face, the lower rear portion of said reflector opposite said front face being parabolic in cross-section and having a parabolic focal line lying within said reflector adjacent the upper limit of said lower portion, the upper portion of said reflector being elliptical in cross-section and having a primary focal line substantially coincident with said parabolic focal line, said upper portion joining said lower portion to form a continuous curved surface extending upward and horizontally` over said focal lines and cornprising a plurality of adjacent elliptic segments shaped and oriented therein to have at substantially the same radial distance from its said primary focal line laterally spaced secondary focal lines lying between said primary focal line and said reflector and positioned in parallel spaced relation with said primary focal line about which they progress sequentially in the same rotational order as their said associated elliptic segments, said lower parabolic portion having an axial plane disposed at a small acute angle below the horizontal thereby to define a main reflected light beam projected downwardly and outwardly from said reflector, and means for mounting in said reflector an elongated tubular light source disposed with its axis substantially coincident with said parabolic focal line.

3. A roadway luminaire adapted to receive an elongated tubular light source and comprising an inverted trough-shaped reflector having a generally spiral transverse cross-sectional configuration, said reflector including an elongated lower parabolic portion at the rear opposite an open front face and including also an elongated upper elliptical portion constituting a top portion of said reflector ad joining said lower parabolic portion to form a continuous curved surface, said lower parabolic portion having a parabolic focal line lying within said top elliptical portion of said reflector and an axial plane disposed at a small acute angle below the horizontal, said top elliptical portion having a primary focal line substantially coincident with said parabolic focal line and comprising a plurality of adjacent elliptical segments having secondary focal lines disposed in substantially parallel spaced relation from said primary focal line and lying along a substantially cylindrical arc within said top portion of said reflector behind said primary focal line, and means for mounting in said reflector an elongated tubular light source disposed with its axis substantially coincident with said parabolic and primary focal lines, whereby all light reflected by said reflector is directed along lines spaced by at least a predetermined minimum radial distance from said parabolic and primary focal lines.

4. A roadway luminaire comprising an elongated inverted trough-shaped reflector having a generally spiral transverse cross-sectional configuration and an open front face, said reflector being disposed with its portion of diminishing radius of curvature forming a top and overhanging front portion and having an inturned reentrant lip at its upper front edge, an elongated transparent cover plate, and a pair of elongated longitudinally slotted connecting bars disposed in interlocking relation between said reflector and cover plate and mounting said plate to enclose said open front face, one said bar interlocking with the inner edge of said reflector lip and having a downwardly sloped surface abutting the bottom of said lip.

5. A luminaire comprising an elongated reflector having a curved transverse cross-sectional configuration and a pair of spaced-apart longitudinal edges defining an open front face, an elongated transparent cover plate, and a pair of elongated connecting bars mounted upon said edges of said reflector and mounting said cover plate to enclose said front face, said connecting bars being slotted longitudinally to receive adjacent edges of said reflector and cover plate in interlocking tongue and groove relation, and a pair of end plates engaging opposite ends of said reflector' and cover plate and connected together by said bars to hold said reflector and cover plate in assembled relation.

References Cited in the file of this patent UNITED STATES PATENTS 1,300,202 Stubblefield Apr. 8, 1919 1,421,058 Barkschat June 27, 1922 1,753,885 Gerhardt Apr. 8, 1930 2,205,310 Robinson et al lune 18, 1940 2,216,084 Libson Sept. 24, 1940 2,297,124 Anderson et al Sept. 29, 1942 2,304,445 Doane Dec. 8, 1942 FOREIGN PATENTS 170,610 Great Britain Oct. 27, 1921 782,163 France Mar. 11, 1933 783,540 France Apr. 8, 1935 100,349 Australia Feb. 22, 1937 477,560 Great Britain Ian. 3, 1938 357,369 Italy Mar. 12, 1938 109,077 Australia Nov. 9, 1939 493,398 Belgium May 16, 1950 669,180 Great Britain Mar. 26, 1952 

